Preventive effect of post-ischemic reperfusion injury by terminal Nicorandil-Mg cardioplegia

In this study, we evaluated the preventive effect of post-ischemic reperfusion injury by Nicorandil-Mg cardioplegia (Nic: 8 mg/l, Mg: 20 mEq/l) given just prior to reperfusion as "terminal cardioplegia". Nineteen dogs were placed on cardiopulmonary bypass and the aorta was cross-clamped for 90 min under hypothermic (17-19 degrees C) cardioplegic arrest. The hearts of ten dogs were reperfused without terminal cardioplegia (Group A). In the other nine dogs, terminal cardioplegia was given for 2 min prior to reperfusion (Group B). During and after a period of ischemia, myocardial tissue calcium ion (t-Ca) and PCO2 (t-PCO2) were continuously monitored by ISFET (ion sensitive filed effective transistor) sensor. Myocardial tissue blood flow, oxygen consumption and lactate flux were calculated at 5, 10, 20, 40 min of reperfusion. And myocardial function was evaluated at 45 min of reperfusion. In the initial reperfusion period, Group B showed an improved myocardial tissue blood flow compared to group A (at 5 min of reperfusion in group A: 29.4% of control, in group B: 42.7% of control, p less than 0.025). T-Ca and T-PCO2 in Group B were rapidly and significantly decreased at 5 min of reperfusion (t-Ca in group A: 2.8 +/- 0.5 mM----1.7 +/- 0.5 mM, in group B: 3.1 +/- 0.6----1.2 +/- 0.4, p less than 0.05; t-PCO2 in group A: 117.5 +/- 23.0 mmHg----82.5 +/- 17.4 mmHg, in group B: 127.5 +/- 22.5----42.5 +/- 9.7, p less than 0.001), and group B had better metablic recovery evaluated by myocardial oxygen consumption and lactate flux.(ABSTRACT TRUNCATED AT 250 WORDS)